This invention relates to securing optical elements to substrates.
Several technologies exist for aligning arrays of optical elements such as optical fibers and ball lenses to provide various photonic devices and fiber blocks. Two examples of such technologies include V-grooves formed in silicon substrates and flexible gripping elements fabricated onto the surface of a variety of substrates.
Silicon V-grooves can be formed by micromachining, etching or other techniques to accurately align the grooves along the crystal planes of a silicon substrate. Typically, V-groove fiber arrays are made by placing optical fibers in V-grooves of a substrate, placing a lid on the fibers, and then securing the assembly with adhesive. The lid can be a substrate containing V-grooves or a flat silicon or glass plate. The adhesive is typically a UV-curable or heat-curable epoxy. Such devices are capable of withstanding compressive and shear forces without deformation. In addition, V-grooves can be reused numerous times, and the fibers can be positioned by sliding fibers within the groove along the axis of the grooves until accurate alignment is achieved. V-grooves can be used to produce 125 micron fiber arrays with spacings as low as 127 microns between fiber centers. Limitations of V-groove technology include limited substrate materials, assembly time, fabrication tolerance, and the requirement of adhesives to complete assembly.
One example of a problem associated with the use of adhesives is that it can be difficult to position optical fibers in conventional V-grooves because adhesive flows into the small spaces between the fibers and V-grooves. Since the adhesive flows into these spaces, the entire length of the fiber is secured to the V-groove chip in a single step. It is not possible to secure the fiber in the V-groove in multiple gluing steps. This is a problem for certain fiber arrays because multiple gluing steps can improve the alignment of optical fibers.
Flexible gripping elements are disclosed in U.S. Pat. Nos. 6,266,472 and 5,359,687. Gripping elements or grippers are versatile structures fabricated from flexible polymeric materials. An example of one way to manufacture grippers includes photolithographic processes, which can be used to form grippers on a variety of substrates. Grippers require less precise dimensional tolerances than V-grooves to hold fibers, and fibers easily snap into, and are held in, place without the use of adhesives. Grippers, however, are limited in that they deform under external forces, they exert frictional forces on the fiber during alignment, which makes alignment more difficult. Furthermore, spacing between fibers is typically limited to about 250 microns.
It would be desirable to provide alignment methods and articles for optical fibers that combined certain advantages of both V-groove and gripper technologies while, at the same time, avoiding certain disadvantages of each of the technologies. Such alignment methods and articles would facilitate the manufacture of a wide variety of optical devices.
Certain embodiments of the invention relate to methods and articles for positioning arrays of objects, for example cylindrical objects such as optical fibers, and spherical objects such as ball lenses, and optical devices including such arrays. Certain embodiments of the present invention provide relatively simple and inexpensive methods and articles for positioning optical fibers and devices comprising optical fiber arrays. According to certain embodiments, the methods and articles do not require adhesives for securing the fibers in the V-grooves. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.